1. Field of the Invention
This invention relates to improvements in a resonator type silencer which is connected to an air intake duct of an internal combustion engine of an automotive vehicle in order to suppress vibration of intake air to be supplied to the engine.
2. Description of the Prior Art
It is well known that generally box-shaped resonator type silencer having a certain volume is disposed to be connected to an air intake duct of an automotive internal combustion engine. The resonator type silencer functions to suppress vibration of intake air by causing air inside the resonator type silencer to make resonance with the intake air vibration. Such a resonator type silencer is usually formed of plastic and is a large-sized part. Accordingly, the resonator type silencer includes upper and lower cases which are independently fabricated. The upper and lower cases are joined to each other to form the resonator type silencer, in such a manner that the open end sections of them are thermally welded or welded upon vibration under a state where the open end sections are brought into contact with each other. Otherwise, the open end sections of the upper and lower cases may be joined by means of clips, screws or the like. Such a technique is disclosed in Japanese Utility Model Provisional Publication No. 6-60764.
However, difficulties have been encountered in the above conventional technique. That is, a large-sized facility for the above-mentioned welding is required thereby increasing a plant and equipment investment. Additionally, in case that the upper and lower cases are joined by means of the clips, screws or the like, such separate parts for joining are necessary, thereby raising a production cost. Furthermore, a slight clearance tends to be formed between the open end sections of the upper and lower cases. This clearance will lower a suppression effect for intake air vibration inside the air intake duct of the engine.